Separation device having a centrifugal rotor

ABSTRACT

In a separation device for separating particles from a liquid, which is present in a container, a centrifugal rotor is rotatable around a vertical rotational axis. The centrifugal rotor has a tubular inlet member, which extends down into liquid to be treated and which upon rotation of the centrifugal rotor forms a pumping member adapted to pump liquid upwardly and into the centrifugal rotor. The rotatable inlet member is surrounded by a non-rotatable wall, a sealing device being adapted to seal between the rotatable inlet member and the non-rotatable wall. Thereby is avoided that liquid is pumped upwardly on the outside of the inlet member. Furthermore, a smallest possible part of the outside of the inlet member can be in contact with liquid, independent of the level of the liquid surface in the container.

FIELD OF THE INVENTION

The present invention relates to a centrifugal separation device forcleaning of a liquid from solid or liquid particles suspended thereinand being lighter and/or heavier than the liquid, the separation deviceincluding a centrifugal rotor adapted to rotate around a verticalrotational axis, a driving device adapted for rotation of thecentrifugal rotor around said rotational axis and a tubular inlet memberwhich is connected with the centrifugal rotor and adapted to extenddownwards from the centrifugal rotor and into a body of said liquidwhich is to be pumped by means of the inlet member into the centrifugalrotor.

BACKGROUND OF THE INVENTION

A separation device of this kind is known for instance through U.S. Pat.No. 1,927,822, U.S. Pat. No. 3,424,375 or EP 0 047 677 A2. Theseparation device can be applied directly onto a container containingthe liquid to be cleaned.

Often it is not possible to keep the liquid surface in a container forliquid to be cleaned constantly at a predetermined level. Upon use of aseparation device of the above said previously known kind the tubularinlet member, in a case like this, will be more or less immersed in theliquid. Since the inlet member has to extend under the liquid surface,when the liquid is at a relatively low level, this means that anundesired large part of the inlet member will be immersed in the liquidwhen the liquid surface is at a relatively high level.

One reason why the rotating inlet member should not be immersed deeperthan necessary in the liquid to be cleaned is that this causes rotationof the liquid in the container. This reduces the pumping effect of theinlet member and causes undesired splitting of particles, which laterare to be separated from the liquid in the centrifugal separator.Another reason is that an unreasonably high amount of energy is requiredto operate the centrifugal rotor.

SUMMARY OF THE INVENTION

This object can be achieved according to the invention by means of anon-rotatable wall, which is adapted to surround in said liquid body atleast part of the rotatable inlet member and a sealing device adapted toseal between the non rotatable wall and the rotatable inlet member.

By the invention it is possible to minimise the surface of the rotatableinlet member being in contact with the liquid to be cleaned,irrespective of at which level the liquid surface is present. Thereby,rotation of the liquid present in the container and which is to bepumped upwardly through the inlet member is minimized. Furthermore, theinvention avoids liquid being pumped upwardly on the outside of theinlet member as a consequence of the rotation of the liquid.

The sealing device may have any suitable construction. For instance, anannular lip gasket of rubber or some other elastic material may besupported by the nonrotatable wall and surround the inlet member andseal radially against the outside thereof. Alternatively, a similarannular lip gasket may be carried by the rotatable inlet member, so thatby means of centrifugal force it can be kept pressed radially outwardlyagainst the surrounding non-rotatable wall.

In a preferred embodiment of the invention the sealing device includesan annular axially movable sealing member and means adapted toaccomplish an axial sealing force between the non-rotatable wall ornon-rotatable members connected therewith and the rotatable inletmember. The sealing member may be rotatable together with the inletmember, but preferably it is non-rotatable and adapted to be pressedaxially against a sealing surface, preferably an end surface of therotatable inlet member.

To achieve the best possible preconditions, as to function, for thesealing device when the centrifugal rotor is suspended from a flexiblesuspension device, the non-rotatable wall is suspended from the sameflexible suspension device as the centrifugal rotor. In this wayrelative pendulum movements between the rotatable inlet member and thenon-rotatable wall are avoided during operation of the centrifugalrotor.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in the following with reference to theaccompanying drawing, in which:

FIG. 1 shows a separation device according to the invention and acontainer containing liquid to be cleaned by means of the separationdevice;

FIG. 2 shows part of the separation device in FIG. 1 on an enlargedscale; and

FIG. 3 is a sectional view taken along line 3—3 in FIG. 2.

FIG. 4 is a sectional view taken along line 4—4 in FIG. 2.

FIG. 5 is a sectional view taken along line 5—5 in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a container 1 having an inlet 2 for liquid to be cleanedand an outlet 3 for liquid having been cleaned from particles suspendedtherein. In the container 1 there is a liquid body 4, in which somerelatively light particles have accumulated in a surface layer and somerelatively heavy particles have accumulated in a bottom layer.

The container 1 has an upper wall 5 having an opening 6. On the wall 5there is mounted a centrifugal separation device according to theinvention and indicated generally by the letter S, which extends downinto the container. The separation device S includes a centrifugal rotor7, an inlet member 8 connected with the centrifugal rotor and a motor 9for rotation of the centrifugal rotor 7 and the inlet member 8 around avertical rotational axis R.

The inlet member 8, which is tubular and slightly conical, is connectedwith the centrifugal rotor by means of a lock ring 10 and extendsdownwards into the container 1, so that it is immersed in the liquidbody 4. Both the centrifugal rotor 7 and the inlet member 8 aresurrounded by a stationary casing 11, which also extends downward intothe container 1, so that it is immersed in the liquid body 4 around theinlet member 8.

The whole separation device S, including the casing 11, is suspendedflexibly in a suspension device 11 a on the upper side of the containerwall 5. Thus, if the centrifugal rotor 7 and its inlet member 8 vibrateor undergo small pendulum movements during operation, the casing 11 willmove in the same way.

Closest to the inlet member 8 the casing 11 forms a cylindricalsurrounding wall 12, which extends from the liquid free part of thecontainer 1 down into the liquid body 4. At its lower part thesurrounding wall 12 carries a sealing device 13 adapted to accomplishsealing between the stationary surrounding wall 12 and the rotatableinlet member 8.

As best seen in FIG. 2, the sealing device 13 includes an axiallymovable sleeve formed sealing member 14. Through an upper part 14 a thesealing member 14 abuts sealingly around its circumference against theinside of the surrounding cylindrical wall 12. By means of a coil spring15, which rests on an annular flange 16 connected with the surroundingwall 12, the sealing member 14 is pressed axially upwardly withreference to FIG. 2. Thereby, a lower part 14 b of the sealing member 14is kept pressed axially against another sealing member 17, which isconnected with the lowermost part of the rotatable inlet member 8. Thesealing members 14 and 17 thus abut against each other throughrespective axially directed sealing surfaces.

Said lower part 14 b of the sealing member 14 has a central throughopening, which is bridged by a wing 18 intended to impede rotation ofliquid present in the container 1 below the separation device. Theextension of the wing 18 is also shown in FIG. 5.

FIG. 3 shows a section through the inlet member 8 along a line 3—3 inFIG. 2. As can be seen, the inlet member has three internal wings 19,which extend both radially and axially through the whole of the inletmember 8 up to the centrifugal rotor 7 (see FIG. 1). The wings 19 areadapted to entrain liquid in the rotation of the inlet member duringoperation of the separation device.

FIG. 4 shows a section through the casing 11 along the line 4—4 in FIG.2. On its outside the casing has wings 20, which extend both radiallyand axially and which have for its purpose to counteract rotation ofliquid in the container 1. As can be seen from FIGS. 1 and 2, there isdelimited in the casing 11 a space 21, which through three channels 22communicates with the interior of the container 1 below the separationdevice.

The centrifugal rotor 7 is not described in detail in the following,since it can be substituted with any suitable centrifugal rotor of aknown kind having a different construction. For a description in detailof a suitable centrifugal rotor reference is made to for instance EP 312233 B1, EP 312 279 B1, WO 96/33021 and WO 96/33022.

In the area of the connection between the inlet member 8 and thecentrifugal rotor 7 there is delimited in the latter an inlet chamber23. Via an inlet channel 24 the inlet chamber 23 communicates with aseparation chamber 25. The centrifugal rotor 7 has an outlet 26 for aseparated relatively light liquid and an outlet 27 for a separatedrelatively heavy liquid.

The surrounding casing 11 has a receiving chamber 28 and an outlet 29therefrom for separated light liquid leaving the centrifugal rotor.Furthermore, the casing 11 has a receiving chamber 30 for separatedheavy liquid leaving the centrifugal rotor. The receiving chamber 30communicates with the aforementioned space 21 in the casing 11.

The above described separation device operates in the following mannerupon cleaning of a liquid containing both liquid particles lighter thanthe liquid and solid particles heavier than the liquid.

When the motor 9 is started for driving the centrifugal rotor 7 and theinlet member 8 connected therewith around the rotational axis R, theinlet member 8 will operate as a pumping member, by means of which theliquid is pumped from the liquid body 4 into the centrifugal rotor.Within the inlet member 8 a substantially cylindrical liquid surfacewill be formed, as illustrated in the FIGS. 1 and 2, which extends allthe way from the lower part of the inlet member to the inlet chamber 23of the centrifugal rotor. In the liquid body thus formed in the inletmember 8 and being entrained in the rotation thereof by the wings 19(see FIG. 3) liquid will flow axially upwardly, as illustrated by meansof arrows in the FIGS. 1 and 2. Centrally in the inlet member 8 there isleft an air filled space, which if desired may communicate with airsurrounding the inlet member 8. For this purpose the inlet member 8 maycarry a thin tube extending from the center of the inlet member radiallyoutwardly to the outside of the inlet member. A pipe of this kind isindicated by dotted lines in FIG. 1 at the upper part of the inletmember 8.

Liquid entering the inlet chamber 23 of the centrifugal rotor 7 throughthe inlet member 8 is conducted therefrom through the inlet channel 24into the separation chamber 25. In this there is arranged a set ofconical separation discs, which between themselves form thin separationspaces. In the separation spaces those particles of different kinds,which are suspended in the liquid, are separated due to the light liquidparticles being forced by the centrifugal force to move towards therotational axis of the centrifugal rotor and, after having coalesced toa continuous phase, further out through the outlet 26, while the heavysolid particles are forced to move towards the radially outermost partof the separation chamber 25, where they deposit on the surrounding wallof the centrifugal rotor. The cleaned liquid first flows in a directionfrom the rotational axis of the centrifugal rotor out of said separationspaces and after that through one or more collection channels againtowards to rotational axis to the centrifugal rotor outlet 27 forseparated relatively heavy liquid.

Whereas separated relatively light liquid is conducted through theoutlet 29 in the casing 11 to a particular recipient, the cleaned liquidis conducted from the outlet 27 back to the liquid body 4 in thecontainer 1. Thus, the cleaned liquid is conducted through the receivingchamber 30 to the space 21 in the casing 11 and from there through thechannel 22 out into the liquid body 4.

If the amount of light liquid separated from the heavier liquid issmall, there is returned to the liquid body 4 a flow of liquid that issubstantially of the same magnitude as that which is pumped therefrominto the centrifugal rotor 7. A certain difference as to level will comeup between the liquid surfaces in the space 21 and the surroundingcontainer 1, respectively, as illustrated in the FIGS. 1 and 2.

The stationary wall 12, which surrounds the inlet member 8 and supportsa part of the sealing device 13, need not necessarily be carried by thecasing 11. The wall 12 alternatively may be carried by the container 1.However, the arrangement shown in the drawing is advantageous for thefunction of the sealing device 13. Thus, it is an advantage that both ofthe co-operating sealing members 14 and 17 are carried by one and thesame suspension device. Since a suspension device for the rotatablecentrifugal rotor 7 should be flexible, and the rotatable part of thesealing device 13 thereby becomes flexibly suspended, also the nonrotatable part of the sealing device should, thus, be flexiblysuspended.

As indicated above a separation device according to the invention may beused for cleaning of a liquid independent of whether the liquid is to becleaned from particles heavier than the liquid or particles lighter thanthe liquid. Of course, the construction of the centrifugal rotor thenhas to be adapted to the separation duty in question. It is alsopossible that the particles—solid or liquid—to be separated from aliquid are more valuable than the liquid itself and that, thus, theseparating operation could not really be named a liquid cleaningoperation. Furthermore, it is not a prerequisite for the invention thatthe liquid having been freed from particles should be returned to thecontainer 1.

1. A separation device comprising: a centrifugal rotor suspended from aflexible suspension device and adapted to rotate around a verticalrotational axis, a driving device adapted for rotation of thecentrifugal rotor around said rotational axis, a tubular inlet member,which is connected with the centrifugal rotor and adapted to extenddownwards from the centrifugal rotor and into a body of liquid, which isto be pumped by means of the inlet member into the centrifugal rotor, anon-rotatable wall which is adapted to surround in said body of liquidat least part of the rotatable inlet member, the non-rotatable wallbeing suspended from the flexible suspension device for avoidingrelative pendulum movements between the rotatable inlet member and thenon-rotatable wall during operation of the centrifugal rotor, and asealing device adapted to seal between the non-rotatable wall and therotatable inlet member.
 2. A separation device according to claim 1,wherein the sealing device includes an annular axially movable sealingmember and means adapted to accomplish an axial sealing force betweenthe non-rotatable wall and the rotatable inlet member.
 3. A separationdevice according to claim 2, in which the annular sealing member isnon-rotatable and adapted to be pressed axially against a sealingsurface on the rotatable inlet member.
 4. A separation device accordingto claim 3, in which an end surface of the rotatable inlet member formssaid sealing surface.
 5. A separation device according to claim 4, inwhich the sealing surface is a generally radial surface.
 6. A separationdevice according to claim 2 wherein the means adapted to accomplish asealing force comprises a spring.
 7. A separation device according toclaim 6 wherein the spring is a coil spring.
 8. A separation deviceaccording to claim 6 wherein the non-rotatable wall has a flange and thespring acts between the flange and the sealing member.
 9. A separationdevice according to claim 8 wherein the non-rotatable wall comprises acylindrical wall coaxially surrounding the inlet member and the flangecomprises an annular flange.
 10. A separation device comprising: acentrifugal rotor adapted to rotate around a vertical rotational axis, adriving device adapted for rotation of the centrifugal rotor around saidrotational axis, a tubular inlet member, which is connected with thecentrifugal rotor and adapted to extend downwards from the centrifugalrotor and into a body of liquid, which is to be pumped by means of theinlet member into the centrifugal rotor, a non-rotatable wall, which isadapted to surround in said body of liquid at least part of therotatable inlet member, and a sealing device adapted to seal between thenon-rotatable wall and the rotatable inlet member and including anannular axially movable sealing member and means adapted to accomplishan axial sealing force between the non-rotatable wall and the rotatableinlet member; said annular sealing member being non-rotatable andadapted to be pressed axially against a sealing surface on the rotatableinlet member and wherein an end surface of the rotatable inlet memberforms the sealing surface.
 11. A separation device according to claim10, in which the sealing surface is a generally radial surface.
 12. Aseparation device according to claim 10 wherein the means adapted toaccomplish a sealing force comprises a spring.
 13. A separation deviceaccording to claim 12 wherein the spring is a coil spring.
 14. Aseparation device according to claim 12 wherein the non-rotatable wallhas a flange and the spring acts between the flange and the sealingmember.
 15. A separation device according to claim 14 wherein thenon-rotatable wall comprises a cylindrical wall coaxially surroundingthe inlet member and the flange comprises an annular flange.